WASHINGTON—Kerry Kennedy placed a picture of her father, the late Senator Robert F. Kennedy, on the lectern before speaking.

“It’s almost impossible to describe the pain of losing your father to a senseless murder,” she said, “or the anger and fear of knowing that that murder might have been avoided if only our leaders had acted to stop the violence.”

The 53-year-old writer and activist was flanked by Martin Luther King III, son of the civil rights leader who was also assassinated. Joined by politicians, entertainers, and victims, they urged Congress to pass “common sense” gun reforms at a news conference Wednesday on Capitol Hill.

Advertisement - Continue Reading Below

The event was sponsored by the advocacy group Mayors Against Illegal Guns, a network of more than 850 executives from cities and towns nationwide calling for heightened gun control. The organization is co-chaired by Boston Mayor Thomas Menino and New York Mayor Michael Bloomberg.

Speakers at the morning news conference called on Congress to enact firearm reforms proposed by President Obama, including universal background checks and bans on assault weapons and high-capacity magazines.

“We’ve endured enough pain,” Kennedy said, adding that her stance on gun control was molded at a young age.

Her uncle, President John F. Kennedy, was shot and killed in Dallas when she was only four. Her father, Robert Kennedy, was murdered four years later in the midst of his 1968 presidential run. Kerry Kennedy—the seventh of 11 children—had to grow up without a dad.

“This is one of murder’s greatest cruelties,” she said. “It leaves the work of love undone.”

Kennedy’s father was gunned down only two months after civil rights icon Martin Luther King Jr. was shot and killed on a hotel balcony in Memphis, Tenn. She ended her call for gun-control legislation by quoting her father’s speech on April 5, 1968, the day after King died.

“Whenever any American’s life is taken by another American unnecessarily...whenever we tear at the fabric of the life which another man has painfully and clumsily woven for himself and his children, the whole nation is degraded.”